Radiant energy generation



A ril 22, 1958 A. D. LA RUE ETAL' 32 RADIANT ENERGY GENERATION Filed May 11, 1955 3 Sheets-Sheet 1 /NVENTORS ALBERT D. LA/PuE Tram/5y April 22, 1958 Filed May 11, 1955 FIG. 2

A. D. LA RUE ETAL RADIANT ENERGY GENERATION s Sheets-Sfieet 2 A 7' TOR/my April 22, 1958 A. D. LA RUE ET AL 2,832,007

RADIANT ENERGY GENERATION 3 Sheets-Sheet 3 Filed May 11, 1955 """III V em United States Patent RADIANT ENERGY GENERATION Albert D. La Rue, Lexington, and Peter J. Lazarkis, Cambridge, Mass., assignors to Raytheon Manufacturing Company, Waltham, Mass, acorporation of Delaware Application May 11, 1955, Serial No. 507,711 6 Claims. (Cl. 315-39.75)

This invention relates to radiant energy, and particularly to the generation of high frequency electromagnetic wave energy in an electron discharge device of the magnetron classification.

The invention is directed to the related problems of leakage current, noise, and runaway that have heretofore been associated with magnetron structures. The invention proposes the correction, or at least the reduction, of these difllculties by providing a novel method and means for preventing current leakage into and around peripheral areas adjoining the working cavities of the magnetron.

The disclosed method includes the step of providing an energy leakage barrier in the form of radiation shielding elements electrically insulated from the electron-emitting cathode, and also electrically insulated from the anode structure and from the polar iron of the mag netrons magnetic circuit.

By establishing the described floating relationship as between the shielding circuit, on the one hand, and the emitting, reflecting and magnetic surfaces, on the other, there is achieved the three-fold advantage of (a) peripheral leakage prevention, (b) electrical and thermal isolation of the shielding circuit, and (c) maintenance of the shielding circuit within a suitable automatically acquired potential range relative to that of the cathodeanode circuit, without the necessity of running conducting leads thereto from an exterior point.

These and other characteristics and advantages of the invention will become apparent upon reference to the fol lowing description of the invention as embodied in the magnetron structure illustrated in the accompanying drawings wherein:

Fig. 1 is an enlarged-scale longitudinal sectional view of an electron discharge device embodying the invention;

Figs. 2 and 3 are transverse sectional views along lines 22 and 3-3, respectively, of Fig. l; and

Fig. 4 is an exploded view of the central sub-assembly of the device.

Referring first to Fig. l, the numeral designates an electrically conductive block-like body, preferably of copper, centrally apertured to provide space for subsequent insertion of a plurality of radially disposed vanes 11 constituting, with the surrounding body 10, the anode structure of an electron discharge device of the magnetron classification. Vanes ll, brazed or otherwise integrated with block Ill, have their inner edges disposed in spaced circular array about the emissive portion 12 of the centrally positioned tubular rod 13 constituting the cathode structure of the magnetron.

The floating end shields of the present invention are shown as constituted by thin metallic discs 26 and 27, and their central tubular extensions 41 and 42, respectively. These shields are supported in spaced relation to the upper and lower surfaces, respectively, of the centrally disposed annular shelf 28 from which the anode vanes 11 project inwardly. By reason of this positioning, the d cs 2d and 27 form barriers dividing the magnetron 2,832,007 Patented Apr. 22, 1958 M body into three superposed chambers 31, 32-, and 33, with the upper and lower chambers 31 and 33 serving as insulation and isolation chambers that are maintained substantially free of electronic charges, while the central chamber 32 includes the vanes 11 and is compartmented by said vanes to form the circular array of sector-shaped resonant cavities receiving electronic emission from the cathode surface 12. Vanes 11 direct this emission toward the arcuate surfaces forming the cavity outer walls, all of which are integral parts of the annular shelf 28. The two end-shields 26 and 27 are spaced from annular shelf 23, on opposite sides thereof, by the provision of spacer bushings 29 and 30 retained in socketed portions of the upper and lower surfaces, respectively, of shelf 28. Retention is effected by inserting screw studs 55 in the three threaded holes angularly spaced about the shelf 28, which holes are previously drilled and tapped. Spacers 29 and 30 are internally threaded to facilitate their retention upon screw studs 55, and also to receive the screws 56 and 57 by which the discs 26 and 27 are secured to the respective sets of spacers.

To facilitate the above-described installation of the end-shields 26 and 27, the disc portions thereof are centrally apertured, and to the circular edges of these apertures are attached tubular posts, 41 and 42, whose inner walls are concentric with the cathode rod 13 but are spaced therefrom sufficiently to insureeffective impedance to thermal and electrical energy transfer therebetween. A similar separation exists between. the posts 41 and 42, on the one hand, and the inner bore surfaces of the polar elements 21 and 22, respectively, so that heat or current transfer therebetween is similarly impeded. If desired, spacers of suitable dielectric material may be inserted in the spaces between the posts and polar elements. One such spacer is indicated at 46, in Fig. 1.

Since the above-described spacers 29 and 30am of insulating material, they serve to complete the electrical isolation of end-shields 26 and 27 with respect to the anode, cathode, and polar elements of the illustrated device; that is, there is no current transfer path from any of these elements which includes the end-shields 26 and 27. Hence the only electrical energy to reach discs 26 and 27 will be in the form of electron emission across the free space surrounding cathode emitting surface 12,

andbounded, above and below said surface, by said discs 26 and 27, respectively.

The thermal isolation and electrical isolation of the end-shields 26 and 27 are of marked significance. Thermal isolation affords the advantage of low operating temperature, which in turn reduces the likelihood of primary emission from the end-shields. Electrical isolation affords the advantage of applying subordinate potential to the end shields, that is, a potential that is either negative or of sufiiciently low positive value, in relation to anode potential, to cause the end shields to serve effectively as leakage impeding means. Also, although the discs 26 and 27 will necessarily absorb some of the heat radiated from the cathode rod 13, such heat absorption will be significantly less than in former devices wherein there was direct contact between end-shield surfaces and the cathode structure; hence operating temperatures for the end-shields will be decidedly lower than in devices heretofore used.

Due to the floating disposition of the end-shields, in relation to the cathode structure, they will quickly absorb sufiicient electronic emission from the cathode to develop their optimum potential, in relation to the cathode and anode potentials, and they will have no difliculty in maintaining such potential, since the absence of any current-conducting contact with either the cathode, the anode, or the polar structures of the magnetron will automatically protect the elements 26, 27 against the possibility of radical potential changes such as would prevail if there were a condition of actual physical contact with other current-carrying elements. Moreover, this susceptibility to the absorption of cathodic emission renders unnecessary the use of the heretofore employed special leadin connections for delivering operating potential to the end-shields from an external energy source.

In addition to polar elements 21 and 22, the magnetic circuit of the magnetron includes bridging iron 23 (Fig.

3), preferably of permanent magnet composition and of horse-shoe contour, with its two extremities lying in juxtaposed relationship to the polar elements 21 and 22, respectively. As indicated in Fig. 3, the magnet 23 is held in this assembled relationship by a combination of threadedly inter-engaged elements 50, 51, 52 and 53 serving to align-the magnet with a counter-sunk radial bore 54 formed in anode body 10. Polar elements 21 and 22 register with nonmagnetic anode caps 24 and 25, respectively.

At one location along shelf 28 the wall of the shelf is apertured to provide an outlet portal 35 facilitating egress of the generated wave energy. An outlet fixture 36 has a circular rim 37 internally threaded for coupling to the externally threaded rim 38 of anode block 10, and constitutes a transition path connecting portal 35 with a suitable wave guide structure (not shown).

Lead-in wires 18 and 19 connect in conventional manner to conductor 14 and cathode rod 13, respectively. Conductor 14 is centered within rod 13 by conventional means (not shown), and serves to supply current to the conventional cathode heater coil within said rod 13.

For cooling purposes fins 60 are formed on one end of anode block 10, each of which fins surrounds the body 10 and removes heat from all four lateral surfaces thereof.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In an electron discharge device, in combination, a cathode element centrally disposed in said device, a plurality of anode elements disposed radially of said cathode element, a series of dielectric supporting elements mounted on said anode disposed in parallelism with said cathode element, and an end shield spanning said dielectric supporting elements and insulated from said cathode.

2. In an electron discharge device, in combination, a cathode element centrally disposed in said device, a plurality of anode elements disposed radially of said cathode element, a surrounding body electrically connecting said anode elements, a series of dielectric supporting elements secured to said surrounding body and disposed in parallelism with said cathode element, and an end shield spanning said dielectric supporting elements and insulated from said cathode.

3. In an electron discharge device, a cathode element centrally disposed in said device, a plurality of anode elements disposed radially of said cathode element, an

- anode block having an annular shelf surrounding said radially disposed anode elements, said shelf dividing said anode chamber into two main compartments, and an end shield insulatedly mounted on said shelf dividing each of said main compartments into inner and outer subcompartments, with said outer sub-compartments being shielded from stray energy reception by said end shields insulated from said cathode.

4. A device as defined in claim 3, wherein said annular shelf is slotted between two of said radially disposed anode elements, to direct energy from said device.

5. A device as defined in claim 3, including magnetic means for directing flux axially of said device, and means engageable with said annular shelf for supporting said anode elements and magnetic means in operative interrelationship.

6. A device as defined in claim 3, including magnetic means for directing flux axially of said device, and means extending radially outward from said annular shelf for retaining said magnetic means and anode elements in operative inter-relationship.

References Cited in the file of this patent UNITED STATES PATENTS 2,458,142 Brown Jan. 4, 1949 2,498,763 McNall Feb. 28, 1950 2,500,430 Pierce Mar. 14, 1950 2,547,503 Smith Apr. 3, 1951 2,549,846 Nelson Apr. 24, 1951 2,599,237 Cuccia June 3, 1952 

